A Novel Approach for Athlete Profiling: The Unilateral Dynamic Strength Index

Bishop, C, Read, P, Lake, J, Loturco, I, and Turner, A. A novel approach for athlete profiling: The unilateral dynamic strength index. J Strength Cond Res 35(4): 1023-1029, 2021-The Dynamic Strength Index (DSI) provides a ratio of the peak force an athlete can produce in both isometric and ballistic tasks. Although the DSI measured during bilateral tests has been examined, unilateral DSI scores have not been reported to date and thus was the aim of the present study. Twenty-eight recreational sport athletes performed 3 trials of a unilateral isometric squat and countermovement jump (CMJ) to measure peak force in each task across 2 separate test sessions. The unilateral DSI was calculated using both left vs. right and dominant vs. nondominant limbs. Good to excellent reliability was shown in the isometric squat (intraclass correlation coefficient [ICC] = 0.86-0.96; coefficient of variation [CV] ≤ 5.7%) and the CMJ (ICC = 0.83-0.93; CV ≤ 5.8%) on both limbs. The DSI showed moderate to good reliability (ICC = 0.71-0.79; CV = 7.54-11.9%). Dynamic Strength Index scores of 0.52-0.55 and 0.55-0.59 were reported on the left and right limbs, respectively, with no significant differences reported between limbs. A significant difference (p = 0.04) was seen for the CMJ between left and right during the second test session only. The dominant and nondominant limbs reported mean DSI scores of 0.53-0.57, and significant differences were evident between limbs in both the isometric squat and CMJ (p < 0.01). This study provides normative data for the unilateral DSI and indicates acceptable levels of reliability, whereas the consistency of individual measures of peak force can be considered good when quantified unilaterally.